Re: Hello Andrew query on BdsSetMemoryTypeInformationVariable

[Andrew Fish <afish@apple.com>]

Forwarding to the edk2 list ....

> On Feb 8, 2019, at 8:28 AM, galla rao <galla.rao80@gmail.com> wrote:
> 
> Hi Andrew,
> 
> Am sorry for direct message!
>  
> There is a function BdsSetMemoryTypeInformationVariable which causes a reset 
> when i enabled Secureboot related drivers
> 
> Any clue why this function is added in EDK2?
> 

Yea it writes a variable that records how many pages of each memory type are used. This variable is read in PEI and used to pass a HOB into the DXE Core. The DXE Core uses these memory buckets to preallocate ranges for each memory type. This scheme prevents memory fragmentation and makes sure the runtime memory regions are in the same location when the system does an S4 resume from disk. 


> is this a serious error, making the PcdResetOnMemoryTypeInformationChange to FALSE will resolve and boots to OS
> 

I think the idea behind that reboot, is the memory map could be different on the next boot and if that was an S4 the S4 could fail. 

Thanks,

Andrew Fish


> shed some knowledge if you are aware of this feature
> 
> Thanks & Regards
> Galla